The Making of Americans

By

Charles C. Mann

July 6, 2012 4:19 p.m. ET

In May, the Oxford geneticist Bryan Sykes planted himself in the media spotlight, announcing a project to hunt for the yeti—the "abominable snowman." Not by trekking into the Himalayas, its rumored home, but by persuading people who claimed to have samples of the beast (hair, skin, blood and so on) to mail them to his laboratory for genetic analysis. If the DNA in the samples didn't match that from any known species, Bigfoot would be declared real. Genetics, Mr. Sykes argued, would settle the dispute over such "cryptic species" once and for all. "Using genetic analysis is entirely objective," he told LiveScience.com. "It can't be falsified."

ENLARGE

Christopher Serra

DNA USA

By Bryan Sykes

Liveright, 368 pages, $27.95

Mr. Sykes is no stranger to the public eye. A "globe-trotting genetic gumshoe" (Wired), he not only became, in 1994, the first researcher to extract DNA from ancient remains—a 5,000-year-old body found intact in an Austrian glacier—but linked it to a modern descendant living in Dorset, England. A year later, he confirmed that recently exhumed Russian bones had belonged to Czar Nicholas II and his family, murdered in the Russian Revolution.

Most notably, perhaps, he formed Oxford Ancestors, the first commercial enterprise to sell personal genetic analyses, in 2001. That same year, he published "The Seven Daughters of Eve," a best seller that argued from genetic evidence that almost all modern Europeans are descended from just seven women—"Ursula," for instance, who lived in Greece about 45,000 years ago, and "Velda," a resident of northern Spain about 17,000 years ago.

Mr. Sykes's latest foray into hereditary history, "DNA USA," is an attempt to provide "a genetic portrait of America" similar to the representation of Europe in "Seven Daughters"—a project that is all but doomed from the start because of Americans' uniquely tangled genealogy.

Most of Mr. Sykes's work is based not on regular DNA, which is found in the nucleus of a cell, but on another type, contained in small bodies called "mitochondria" that float around by the thousand in the goo between the nucleus and the outer cell membrane. Scientists like mitochondrial DNA because it is plentiful and simple—it contains about 16,000 "bases" (the subunits out of which DNA is constructed), as opposed to the three billion bases in nuclear DNA. Happily for geneticists, mitochondrial DNA (mtDNA) is usually transmitted unaltered from mother to daughter.

Thus, in theory, every woman should have exactly the same mtDNA as her umpteen-greats-grandmother. In fact, though, mtDNA, like regular DNA, gradually accumulates mutations—small changes in the order or composition of the bases. Two people who share a common female ancestor will thus have almost identical patterns of bases, with the differences being attributable to the buildup of mutations over time. In the past, when humans didn't move around quickly, individual areas would come to be dominated by people from the same mtDNA lineage, forming what Mr. Sykes calls "clusters" or "clans," all of whose members descend from a single female ancestor.

Moreover, mtDNA offers clues as to when people moved around. Geneticists say that DNA picks up those small mutations at a roughly steady rate. Thus by comparing the number of differences in a given mtDNA snippet from two people, researchers can estimate how long ago they had a common ancestor. In "Seven Daughters," Mr. Sykes examined the mtDNA of hundreds of Europeans, noted the similarities and differences, and broke the continent into seven clusters, each with its own female ancestor. Each had split off from the others at various points in the past.

The United States is far more genetically scrambled—a crazy quilt of immigrants from every corner of Europe, Africa and Asia laid over a foundation of indigenous Americans. Complicating matters still further, these separate peoples have all bred with each other, willingly or unwillingly, covertly or overtly—think of Sen. Strom Thurmond, the vehement segregationist who fathered a secret child with his 16-year-old African-American maid. Deriving a statistically valid portrait of this jumble, as Mr. Sykes realized, requires taking DNA samples from a gazillion people, an effort that "would have cost millions," take years, "and anyway would only replicate what others had already done."

Faced with this problem, Mr. Sykes punted. He decided to "be guided by chance events from the start: I would just see where they led." As a guiding image, he invokes "Easy Rider" (1969), in which Jack Nicholson and Peter Fonda "wander aimlessly around the southwestern United States." Some readers' hearts will leap at the prospect of following a writer with no intended plan or outcome for 350-plus pages. Alas, I am not one of them.

This scattershot method, unsurprisingly, produces scattershot results. In his "first movement," Mr. Sykes examines the "original ancestral homelands from which Americans have come." Except that he doesn't. The author's America consists exclusively of Indians, Europeans, Africans and Jews. Latinos (16% of the population) and Asian/Pacific Islanders (5%) are left out, as are those who describe themselves to the Census Bureau as "other" (10%). His geography is equally incomplete. In his "second movement," Mr. Sykes rambles across the United States, taking DNA samples, hoping something of interest will turn up. Almost gleefully, he manages to avoid the entire Southeast, taking as a substitute an encounter in San Francisco with two African-Americans from Atlanta.

The people Mr. Sykes seems really interested in, the subject of eight of the 19 chapters in "DNA USA," are indigenous Americans. Understandably so—mtDNA is one of the best tools for getting at the vexed question of Indians' origins, a question that has bedeviled Western researchers for centuries. (Native people tend to be less intrigued, at least in my limited experience. When I have asked the where-are-you-from question, the response has generally been a finger pointing to the ground: "Here.")

Genetically speaking, Native Americans have four main mtDNA clusters, which geneticists have prosaically labeled A, B, C and D. "All have their closest matches in Asia," Mr. Sykes says: three in Siberia and one in China and Taiwan. Geneticists take this as proof that indigenous people crossed over from Asia to the Americas, perhaps across the Bering Strait land bridge.

In 1997, though, geneticists found a fifth cluster, which they labeled X. "There is no trace of any cluster X sequences in Siberia or Alaska," Mr. Sykes says. But "I had often come across cluster X in my work on European mitochondrial DNA, and even recruited it to be among the Seven Daughters of Eve." When combined with other data, Mr. Sykes argues, these findings indicate that "cluster X was in America . . . well before Europeans arrived in large numbers." This suggests that some Europeans migrated to the Americas thousands of years ago and became the ancestors of some native people.

Suggests—but not proves. A recurring annoyance in "DNA USA" and other popular genetics books is that genetic tests are much less definite—and their implications much less clear—than researchers like to pretend. In April 2006, for example, Mr. Sykes's Oxford Ancestors, his genetic-analysis company, proclaimed that a Florida accounting professor was directly descended from Genghis Khan (they had almost identical Y chromosomes). A world-wide buzz ensued.

Before taking a plane to Mongolia, his newfound homeland, the professor checked his DNA at another company. No way! said Firm No. 2—correctly, as Mr. Sykes later agreed. Oxford Ancestors had tested the professor's Y chromosome in nine mutation-prone locations. Seven of the nine places matched. Because Mr. Sykes had never seen such a close fit outside Asia, he announced a direct relationship. The second company found no match at another, less changeable section of the professor's Y chromosome, invalidating the first finding. The professor canceled his vacation in Ulan Bator.

Both companies tested only tiny snippets of DNA and made assumptions about the likelihood that small differences would occur in those snippets. Unfortunately, this practice is all too common. The claims in both "Seven Daughters" and "DNA USA" implicitly depend on the assumption that changes pile up in mtDNA at a consistent rate. But for more than a decade scientists have been arguing about whether this is true. The rates in studies based on comparing close relatives' mtDNA, for example, are roughly three times higher than estimates made by examining large groups within the species. Remember "Ursula," one of the seven daughters who lived in Greece 45,000 years ago? Maybe it was only 15,000 years ago. And maybe it wasn't Greece. Most geneticists today, having more information than Mr. Sykes did in 2001, divide Europeans into 10 to 12 clusters, with different borders.

"DNA USA" gives few hints that cluster X, the purported European mtDNA, has been the subject of long scientific debate. Entirely unmentioned is that in 2001 Russian scientists found cluster X in Altaian peoples from southern Siberia. Or that well-known Brazilian geneticists have argued that "X, together with the other four main mtDNA [clusters], was part of the gene pool of a single Native American founding population" from Asia, as they put it a few years ago in the American Journal of Human Genetics. Cluster X may be a sign that Indians have significant European ancestry, as Mr. Sykes advocates. But readers would be better off if he admitted that most of his colleagues regard the notion as poppycock.

Here, regrettably, Mr. Sykes is in good company. All too often, scientists who write for the public put on their white coats of authority and fail to acknowledge when they are expressing a minority view. Perusing "Guns, Germs and Steel" (1997) one cannot know that many of Jared Diamond's fellow geographers vehemently dispute his ideas. E.O. Wilson's "Social Conquest of Earth," now on best-seller lists, never tells readers that his proposed revision to evolutionary theory, group selection, has been the subject of an intellectual quarrel since V.C. Wynne-Edwards first proposed it in 1962. Wynne-Edwards isn't even in the index to Mr. Wilson's book. Nor are George C. Williams and John Maynard Smith, Wynne-Edwards's principal detractors. Journalists are rightly slapped if they extol an idea and neglect to mention criticisms. Scientists should be, too.

—Mr. Mann is the author, most recently, of "1493: Uncovering the New World Columbus Created."

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